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� <br />�-=i,': ���'ti &;^11L�U�!.I°JC. <br />� <br />cxccedcd \1'ashington Modcl Toxics Controi Act (MTCA) Mcthod A cicanup criteria. Initial <br />� laboratory results furthcr indicated that the detcctcd pctroleum appcarcd to bc wcathcred <br />gasolinc. Thc cm�ironmcmal laboratory .malytical rcports arc includcd in Appendix C. <br />� 5.2 Tolim��-up Soi17'csting <br />� During drilling of borings B-12A. B-I Sr1, and E3-IGB �vc collcctcd onc soil samplc from B-l6A <br />for analytical testing (pctrolcum hydrocarbons and Icad), and found a low conccntration of <br />� wcathcrcd gasolinc (scc Table 1). During drilling of boring B-18, field screcning indicated that <br />potcntiaily contaminated soil was prescnt from about 25 to 42 feet Ugs (approximate clevation <br />l31 to I 14 fcet). Thc mcasurcd groundw:ucr Ievcl at this loca�ion is at approximateiy 30 fect bgs <br />� (approximatc cicvation 136 fect). T���o soil samplcs wcrc collcctcd from B-1 S for analysis. <br />RCSUIlS 10(IIC.IIC lll:ll \Vcathcrcd gasolinc is present at about elevation 126 fcet (30 feet Ugs) at <br />� 2,900 milligrams per kilograms (mg/kg), escceding MTCA Mcthod A cica��up critcria. No <br />bcnzcnc, toluenc, c���ylbcnzenc, or xylcnes ([3TBY) wcrc detectcd. Gi��cn this clevatcd <br />� concentration of weathered gasoline, it seems likcly that a contaminant source is, or �eas, located <br />in thc inuncdiatc vicinity. <br />� 5.3 Ground�vxlcr Sam�iling and Anah�sis <br />Thrcc groundwatcr samples �acrc collccted from monitoring ���ells B-14, B-17 and B-18 on Juh� <br />� 3, 2002, and submiUcd for pclrolcum hydrocarbon analytical tcsting. No contaminants of <br />conccrn wcrc dctcctcd in 13-17. llowc��cr, results indicatc that gasolinc conccnlrations excecd <br />� MTCA Mcthod A dccmup critcria for ground���atcr in wclls B-14 and B-1S. Conccntr:itions of <br />benrenc and cthylbcnzcnc in I3-I S growidwatcr also excced cicanup critcria. <br />� <br />� <br />I3ascd on discussion with thc analytical tcsting laboratory, pctrolcum dctcctcd in groundwater at <br />both wclls B-lS and B-l�l appc:us to bc simil:u• product, although the pctrolcum chromatogram <br />for ���cll B-1S cxhibits morc wcathcring. This indic:ucs th:�t contamination at the two loccuions <br />proUably originatcd from thc samc sourcc. <br />Cr.O 111'llROGI:OLOCIC'I'GS7'ING <br />� Slug testing n�as perfonned to estimate the h}'draulic conductivity of the site soils. Slug tests <br />providc a point cstimatc of hydr:�ulic conducti��ity in the immediatc vicinity of die tcsted wcll; <br />! thcy do nut �nu� i�lc an cstima�c of aquifcr hl'cir:wlic conducti��ity on a largc sc:ilc or an indication <br />i.i_ou�,��.ta�s.r.i-,�i, n�i 2I -1-09G4�-00$ <br />